For many scientists who study it, religion should be placed into one of two camps: 1) religion is an aberration, a mental virus; or 2) religion is an adaptation–that religion enhanced the survival of Believers.  A well-written article by Robin Marantz Henig explores this issue in the New York Times.  The title is “HeavenBound: a Scientific Exploration of How We Have Come to Believe in God.” Henig sums up the alternatives by reference to blood.  A trait might be “adaptive,” like the ability of blood cells to transport oxygen.  On the other hand, a trait might be simply a byproduct, such as the “redness” of blood.

Is blood prominent because it’s red or because it actually carries oxygen?

Several notable scientists and philosophers lead the charge from the first camp (that religion is a byproduct).  One of them is Richard Dawkins, who argues that “religion is nothing more than a useless, and sometimes dangerous, evolutionary accident.”  Others falling into this camp include Sam Harris, Scott Atran, Pascal Boyer and Daniel Dennett. These believers in religion as a “byproduct” would also include Stephen Jay Gould, who proposed the use of the term “spandrel” to describe traits that have no adaptive value of their own.

If religion is a byproduct or a “spandrel,” of what is it a byproduct or “spandrel” of?  Psychologists have looked carefully at several candidates: agent detection, causal reasoning and theory of mind.

We see agents everywhere, it turns out, even in inanimate objects.  The byproduct argument is …